1. Field of the Invention
The present invention relates to a gyroscopic apparatus and an electronic apparatus including the same, such as a gyroscopic apparatus used for detecting a vehicle rollover, vehicle attitude, and camera movement caused by shaking, vibration or an unsteady hand and to an electronic apparatus including such a gyroscopic apparatus.
2. Description of the Related Art
Various types of gyroscopic apparatuses used for detecting a vehicle rollover, vehicle attitude, and camera movement or vibration have been proposed. For example, Japanese Unexamined Patent Application Publication No. 7-332988 discloses a gyroscopic apparatus including a gyro sensor which uses a vibrator that is constructed by attaching two piezoelectric substrates which are polarized in opposite directions.
In this gyro sensor, the vibrator which is held in the air by a supporting member is caused to bend and vibrate in the thickness direction (the same as the thickness direction of the piezoelectric substrates) while both ends thereof are free. When an angular velocity is applied to the gyro sensor in the longitudinal direction (the same as the longitudinal direction of the piezoelectric substrates) as a rotation axis, bending vibrations in the vibrator width direction are generated by a Coriolis force. From the bending vibrations, the direction and magnitude of the angular velocity are detected.
FIG. 16A is a perspective view of a known gyroscopic apparatus, and FIG. 16B is an elevation view of the known gyroscopic apparatus. Referring to FIGS. 16A and 16B, a gyroscopic apparatus 1 includes a gyro sensor 2. The gyro sensor 2 includes a stem 3 which has pin terminals 3a, a cover 4 mounted on the stem 3, and a vibrator 5 which is a vibrating mass arranged in the interior of a casing sealed by the stem 3 and the cover 4. The vibrator 5 is located at a position that is offset from the stem 3 in the casing. Descriptions of a supporting member for supporting the vibrator 5 in the air and a circuit portion for causing the vibrator 5 to vibrate and for processing a signal output from the vibrator 5 are omitted.
FIG. 17 shows the structure of the vibrator 5. The vibrator 5 is formed by attaching, with an intermediate electrode 5F therebetween, a piezoelectric substrate 5U which is polarized in the thickness direction and which contains detecting electrodes 5L and 5R on a first major surface thereof and a piezoelectric substrate 5D which is polarized in the thickness direction and which contains a common electrode 5C on a first major surface thereof, thus bonding second major surfaces of the piezoelectric substrates 5U and 5D.
By applying a drive signal to the common electrode 5C, the vibrator 5 generates both-end-free bending vibrations in the thickness direction (the same as the thickness direction of the piezoelectric substrates 5U and 5D). By applying an angular velocity to the vibrator 5 in the longitudinal direction (the same as the longitudinal direction of the piezoelectric substrates 5U and 5D) as a rotation axis (rotation detecting axis), the Coriolis force generates both-end-free bending vibrations in the width direction (the same as the width direction of the piezoelectric substrates 5U and 5D). Due to the bending vibrations in the width direction, signals in opposite directions are generated at the detecting electrodes 5L and 5R. From these signals, the magnitude and the direction of the angular velocity can be detected.
Referring again to FIG. 16B, when an impact is applied to the gyroscopic apparatus 1 constructed as described above in the direction indicated by the outline arrow, since the vibrator 5 is arranged at an offset position, the vibrator 5 is temporarily displaced to a vibrator 5xe2x80x2 of FIG. 16B due to an elastic deformation of the supporting member and deformation of a cushion. For example, when the gyroscopic apparatus 1 is installed in a vehicle, such an impact is generated in the vertical direction of the vehicle caused by unevenness of a road surface. Although not shown, when the direction of the impact is reversed, the displacement of the vibrator 5 is also reversed. Since the displacement includes a rotational component indicated by the arrow in FIG. 16B, the output of the gyro sensor fluctuates. The larger the offset (positional offset) of the vibrator 5 in the casing defined by the stem 3 and the cover 4, the more noticeable the fluctuation becomes.
FIG. 18 shows the relationship between the acceleration of impact applied randomly to the gyroscopic apparatus 1 arranged as described above in the direction indicated by the outline arrow of FIG. 16B and the output of the gyroscopic apparatus 1. An angular velocity applied to the gyroscopic apparatus 1 is constant. As is clear from FIG. 18, the output of the gyroscopic apparatus 1 fluctuates greatly in accordance with the impact, and the output includes an error signal. It is understood that the output of the gyroscopic apparatus 1 is susceptible to the impact.
When the output of the gyroscopic apparatus 1 includes an error signal, an accurate angular velocity cannot be detected.
In order to solve the foregoing problems, preferred embodiments of the present invention provide a gyroscopic apparatus that is capable of detecting an accurate angular velocity even when an external impact is applied thereto and an electronic apparatus including such a novel gyroscopic apparatus.
According to one preferred embodiment of the present invention, a gyroscopic apparatus includes first and second gyro sensors having substantially the same structure, and an adder for adding the outputs of the first and second gyro sensors. The first and second gyro sensors are arranged so that signals output in response to an angular velocity applied thereto have the same sign and that signals output in response to an impact applied thereto have the opposite signs.
The first and second gyro sensors may be arranged to have an approximately 180-degree rotation symmetry about a virtual rotation axis which is arranged in the direction of rotation detecting axes.
The second gyro sensor may be arranged at a position defined by parallel translating the first gyro sensor which is rotated by approximately 180 degrees about a virtual rotation axis which is in the direction of rotation detecting axes.
A gyroscopic apparatus according to another preferred embodiment of the present invention includes first and second gyro sensors having substantially the same structure, and a subtracter for obtaining the difference between the outputs of the first and second gyro sensors. The first and second gyro sensors are arranged so that signals output in response to an angular velocity applied thereto have the opposite signs and that signals output in response to an impact applied thereto have the same sign.
The first and second gyro sensors may be arranged to have an approximately 180-degree rotation symmetry about a virtual rotation axis that is substantially perpendicular to the rotation detecting axes.
The second gyro sensor may be arranged at a position defined by parallel translating the first gyro sensor which is rotated by approximately 180 degrees about a virtual rotation axis that is substantially perpendicular to the rotation detecting axes.
The gyroscopic apparatus may further include a mounting base, wherein the first gyro sensor may be disposed on a first major surface of the mounting base and the second gyro sensor may be disposed on a second major surface of the mounting base.
The gyroscopic apparatus may further include a mounting base, wherein the first and second gyro sensors may be disposed on one of the surfaces of the mounting base.
The first and second gyro sensors may include vibrating gyroscopes having vibrating masses.
An electronic apparatus according to another preferred embodiment of the present invention preferably includes a gyroscopic apparatus according to the preferred embodiments described above.
With a gyroscopic apparatus constructed according to various preferred embodiments of the present invention, a highly accurate output can be obtained in response to an impact from a specific direction. Also, the performance of an electronic apparatus includes such a novel gyroscopic apparatus is greatly improved.